The known ultrasonic welding device in prior art is a device that converts ultrasonic wave electrical energy from an ultrasonic wave generator into mechanical vibratory energy by a convertor (ultrasonic wave oscillator) and supplies this mechanical vibratory energy to an ultrasonic vibration transmitter (a horn) after amplification with a booster; after resonating in mechanical vibrations at the horn, frictional heat occurs on workpieces by the mechanical vibratory energy of this resonance imparted to the workpieces, and the workpieces are welded by the frictional heat occurring on the workpieces. These ultrasonic welding devices fall into the classification of those that render plastic welding and those that render metal welding. Also, the ultrasonic vibration transmission mechanism (ultrasonic stack) is constructed with the booster and the horn in the above-mentioned ultrasonic welding devices. The ultrasonic vibration transmitter structure (ultrasonic stack) may also include a construction that adds a converter to the booster and the horn.
Various kinds of construction have been proposed in the prior art for a structure that holds this ultrasonic vibration transmitter structure (ultrasonic stack), depending on whether it is to be used for plastic welding or metal welding.
However, on the metal surface in the above-mentioned ultrasonic vibration transmitter, there is no vibration zero point, and the entire surface vibrates. The vibration zero point called the nodal point exists only on the 1 axial point (in brief, the interior horn material), and vibration is zero is in all directions, axial and rectangular. Generally, this is called a node; however, the amount of bulge vibration of the surface is at a maximum. This amount increases for the horn shape and has a greater amplitude in relation to Poisson's ratio, as the diameter is large in the case of a controlling cylindrical rod and as the sheet is thick in the case of the sheet. Therefore, the holder of the ultrasonic vibration transmission mechanism cannot be operated easily, even by using a node; wherefore, various holding methods have been proposed previously.
The representative holding structure of an ultrasonic vibration transmission mechanism for plastic welding, as discussed in paragraphs [0040] and [0041] of Patent Reference 2, proposes a holding structure that disposes a flange in a unified manner on the horn or booster, uses an elastic member such as a rubber O-ring or heat resistant plastic sheet and holds the horn or booster in a support framework by inserting one or both faces of the flange by means of the elastic member. It is necessary that this holding structure be a structure that holds the horn or booster in a support framework by an axial 1-point support. This means that the holding place is a single axial position, and, when supported there, even a construction that temporarily supports this place with several support frameworks, is called a 1-point support. Another example of a holding structure that is a 1-point axial support of an ultrasonic vibration transmission mechanism proposes a holding structure that disposes an S-shaped flange in the booster and holds the booster in the frame by the S-shaped flange (Patent Reference 3, Patent Reference 4).
FIG. 7 is an oblique view showing a typical holding structure with an S-shaped flange of the abovementioned prior art. FIG. 8 is a side view showing a typical holding structure with an S-shaped flange. In FIGS. 7 and 8, the horn 50 has a prescribed length and is formed as a rectangular column on the top side shown in FIG. 7 and the top side in FIG. 8 approximately in the middle of it; when the bottom side shown in FIG. 7 and the bottom side shown in FIG. 8 gradually taper over a prescribed length from approximately in the middle, it takes on a uniform thickness after reaching a prescribed thickness. At the approximate middle of the horn 50, as shown in FIGS. 7 and 8, an S-shaped flanged 60 is disposed. The horn 50 constructs a holding structure by means of the S-shaped flange that is being held fast to a holder not shown in the figures.
On the other hand, for the holding structure of an ultrasonic vibration transmission mechanism for metal welding, support by such a plastic sheet elastic member is insufficient, wherefore a holder by means of metal contact is desirable. However, even with a holding element by metal contact, a spring construction is necessary to absorb the bulge vibrations on the holder. For this reason, it would be necessary to reduce vibration leaks after affixing the holder to an actuator. When there is metal contact, there is generally a support at 2 places separated axially, so that the increased pressure on the horn (pressure added to the workpiece) is rectangular, as opposed to axial.
Concretely, as mentioned in Patent Reference 5, a holding structure is proposed that fixes to a support with support members in two places of the anti-node that arises on the horn (resonator), that is on two anti-nodes at a distance of one wavelength of the ultrasonic wave oscillation on the horn, and, as mentioned in Patent Reference 6, a construction by inserting disk-shaped metal flat plates called diaphragms on two anti-nodes on the booster—that is, on two anti-nodes at a distance of one-half wavelength of the ultrasonic wave oscillation on the booster.
As stated in Patent Reference 7, a holding structure is proposed that disposes an S-shaped spring structure in the vicinity (length of one-half wavelength) of the amplitude zero of the ultrasonic wave horn and is fixed to a frame with such S-shaped spring construction.
Furthermore, as stated in Patent Reference 8, a holding structure is proposed that disposes a booster one wavelength behind the horn and is held to a support via a flange on the node of the respective rear booster [positioned at 1 and a half wavelengths (1.5 wavelengths)].
Each of the holding structures proposes a construction that holds the horn or booster at two place separated axially by one-half wavelength or 1.5 wavelengths.